With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Because aeroel...
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With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Because aeroelastic effects can significantly impact the design of these aircraft, there is a strong need in the aerospace industry to predict these interactions computationally. Such an analysis in the transonic regime requires high-fidelity computational fluid dynamics (CFD) analysis tools, due to the nonlinear behavior of the aerodynamics, and high-fidelity computational structural dynamics (CSD) analysis tools. Also, there is a need to be able to use a wide variety of CFD and CSD methods to predict aeroelastic effects. Because source codes are not always available, it is necessary to couple the CFD and CSD codes without alteration of the source codes. In this study, an aeroelastic coupling procedure is developed to determine the static aeroelastic response of aircraft wings using any CFD and CSD code with little code integration. The procedure is demonstrated on an F/A-18 stabilator using NASTD tan in-house McDonnell Douglas CFD code) and NASTRAN. In addition, the Aeroelastic Research Wing is used for demonstration with ENSAERO (NASA Ames Research Center CFD code) coupled with a finite element wing-box code. The results obtained from the present study are compared with those available from an experimental study conducted at NASA Langley Research Center and a study conducted at NASA Ames Research Center using ENSAERO and modal superposition. The results compare well with experimental data.
The paper describes numerical simulations for hyperbolic heat-conduction problems involving non-Fourier effects via explicit self-starting Lax-Wendroff-based finite element formulations. For cases involving extremely ...
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The paper describes numerical simulations for hyperbolic heat-conduction problems involving non-Fourier effects via explicit self-starting Lax-Wendroff-based finite element formulations. For cases involving extremely short transient durations or for very low temperatures near absolute zero, the classical Fourier diffusion model for heat conduction breaks down since the wave nature of thermal energy transport becomes dominant. Major difficulties in numerical simulations include severe oscillatory solution behavior in the vicinity of the propagating shocks. The present paper describes an alternate methodology and different computational perspectives for effective modeling/analysis of hyperbolic heat-conduction models involving non-Fourier effects. In conjunction with the proposed formulations, smoothing techniques are incorporated to stabilize the oscillatory solution behavior and to accurately predict the propagating thermal disturbances. The capability of exactly capturing the propagating thermal disturbances at characteristic time-step values is noteworthy. Numerical test cases are presented to validate the proposed concepts for hyperbolic heat-conduction problems.
This paper is concerned with the modeling of flexible multibody systems by a Rayleigh-Ritz based substructure synthesis method, so that certain advantages can be accrued by using the variational approach to derive the...
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This paper is concerned with the modeling of flexible multibody systems by a Rayleigh-Ritz based substructure synthesis method, so that certain advantages can be accrued by using the variational approach to derive the eigenvalue problem. As with the classical Rayleigh-Ritz method, if the admissible functions used to represent the motion of the substructures are not chosen properly, convergence can suffer. This paper presents a new substructure synthesis method with superior convergence characteristics achieved by representing the motion by means of a recently developed class of functions, namely, the class of quasi-comparison functions. This improved convergence is shown to be related to improved approximation of both the differential equations and the natural boundary conditions. The theory is demonstrated by means of a numerical example.
A new method of modeling frequency-dependent material damping in structuraldynamics analysis is reported. Motivated by results from materials science, augmenting thermodynamic fields are introduced to interact with t...
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A new method of modeling frequency-dependent material damping in structuraldynamics analysis is reported. Motivated by results from materials science, augmenting thermodynamic fields are introduced to interact with the usual mechanical displacement field. The methods of irreversible thermodynamics are used to develop coupled material constitutive relations and partial differential equations of evolution. These equations are implemented for numerical solution within the computational framework of the finite-element method. The method is illustrated using several examples including longitudinal vibration of a rod, transverse vibration of a beam, and vibration of a large space truss structure.
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